1. Field of the Invention
The present invention relates to a computer system and more particularly to logical partitioning technology which involves storages of computer systems connected with storage systems.
2. Description of the Related Art
One approach to improving the performance of an information processing system is to increase the number of computers in an information processing system. However, the use of many computers in a system poses the following problem: it necessitates a troublesome task of controlling individual computers, requires a larger footprint for the computers and consumes more electric power. As a solution to this problem, technology which logically partitions resources of a computer with a large processing capacity (LPAR: Logical Partitioning) and makes it possible to use resulting logical partitions as independent virtual computers has been proposed. This logical partitioning technology can make one computer look like a plurality of virtual computers. When allocation of resources (processor, memory, etc.) to partitions is controlled, the performance of each virtual computer is assured. With this technology, different operating systems can be freely installed in virtual computers so that each virtual computer can be turned on and off or troubleshot independently for flexible operation. In addition, the use of a smaller number of physical machines offers advantages in terms of system control, footprint and power consumption. This kind of logical partitioning technology is disclosed, for example, in JP-A No. 157177/2003 (patent literature 1).
In the logical partitioning technology which has been used so far for computers, resources of computers such as processors and memories are logically partitioned and allocated to virtual computers.
Storage systems which are used with computers include not only a storage system directly connected with a host computer but also a storage system shared by plural computers through a network. The memory area of a storage system connected with a computer is partitioned and one of resulting partitions is allocated to one of the virtual computers.
When a storage system has a file system function, it is used as a storage system which allows sharing of files among different servers, namely NAS (Network Attached Storage) as a storage system which is file-accessible from a computer. Data communication between a NAS and a host computer takes place file by file where each file should have a name and a structure which the operating system running on the host computer recognizes. For this reason, in addition to a disk drive which stores data and its controller, the NAS has a processor and a memory for operation of a file system which converts file input/output with the host computer into data input/output with the disk drive. This type of NAS does not take logical partitioning of resources into consideration.
Besides, a RAID (Redundant Array of Independent Disks) system, which is used with a large external storage system, does not presuppose logical partitioning. Even when logical partitioning is permitted in this type of RAID system, a server system just performs logical partitioning of pre-allocated storage resources and cannot reallocate the resources of the storage system and therefore allocation of resources of the whole system including the server system and storage system cannot be optimized.